DCHAS-L Discussion List Archive

I disagree with amorphous silica being cited as a "nuisance dust".

Independent of any toxicity issues, amorphous silica is a regulated substance by OSHA as per 29 CFR 1910.1000 (see table z-3). However, I believe that this is rarely (if ever) enforced. Even though there are reasonable arguments that this OSHA PEL reference value is outdated and may not be relevant - it is still the law.

The OSHA PEL is a calculated value that is based off of the percent of amorphous silica material in the particulate: 80 mg / % amorphous silica.

Many people are confused by this formula as they incorrectly think that the % silica in the formula is for crystalline silica.

If working with 100% amorphous silica, the PEL would 0.8 mg per cubic meter.

This is the one and only instance that I have noted that the OSHA PEL is actually lower than ACGIH TLV or NIOSH REL values.

See links below if interested in learning more:

http:​//www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id™94

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=25740

Keith Rickabaugh

Technical Director, Materials & Analytical Services

RJ Lee Group
www.rjlg.com

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